A power system is constructed by connecting power generation equipment and load equipment by a power transmission facility. There are power systems in various scales from a large-scale system connecting a plurality of large-scale power plants and many factories, commercial facilities and households to a small-scale system constructed within a specific facility.
One type of power generation equipment includes a power generation system utilizing natural energy such as sunlight and wind power. The power generation system utilizing the natural energy is being widely introduced in response to rise in awareness of energy problems and environmental problems in recent years. However, the power generation system utilizing the natural energy has a disadvantage that power cannot be stably supplied since generated power tends to be controlled by natural factors such as seasons and weather. In order to make up for the disadvantage, the power generation equipment for which a power generation system and a storage battery system are combined is being considered.
The storage battery system is used as a means for stabilizing power supplied to a power system by the power generation equipment. It was thought before that it is difficult to store a large amount of power, however, since a storage battery of a large capacity such as a lithium-ion battery and sodium-sulfur battery is put into practical use, it is made possible to store the large amount of power. By connecting the storage battery system including such a storage battery to the power generation system, an operation is possible in which excess power is charged in the storage battery when supply is excessive in contrast with power demand, and power insufficiency is compensated by discharge from the storage battery when the supply is insufficient in contrast with the power demand. By combining the storage battery system with the power generation system utilizing the natural energy, the generated power that fluctuates depending on seasons and weather or the like is leveled by charge/discharge of the storage battery, and the power can be stably supplied to the power system.
Note that the applicant recognizes a literature described below as the one associated with the present invention. Patent Literature 1 discloses a configuration that a photovoltaic power generation system and a storage battery system are connected and fluctuation of generated power of photovoltaic power generation is suppressed by charge/discharge control of a storage battery.